The invention relates to a method of preparing a catalyst showing a zeolitic-structure, containing silicon and titanium, particularly suitable for the ammoximation of carbonylic compounds in trickle bed reactors.
It is known, from German patent No. 1,245,371, to obtain cyclohexanone-oxime by catalytic reaction in the liquid phase of cyclohexanone with ammonia and hydrogen peroxide ("ammoximation reaction"), at a temperature from 5 .degree. to 40.degree. C. and according to suitable ratios of the reactants to each other, in the presence of a catalyst consisting of phospho-tungstic acid or similar compounds. A drawback of this method is however that this type of catalyst is difficult to handle, above all during the separation of the product from the catalyst. European patent publication 208,311 in the Applicant's name, teaches that an effective alternative can be residing in the catalysis by a synthetic, crystalline, porous material based on silicon and titanium oxides (titanium-silicalite); see also, in this connexion, U.S. Pat. No. 4,410,501 and European patent publication Nos. 132,550 and 190,609. The Applicant has also found that a special post-treatment type (with H.sub.2 O.sub.2) of titanium-silicalites endows these latter with exceptional, and at all surprising catalytic properties in the reaction of ammoximation of various carbonylic compounds (see European patent application No. 87/108,577) and that the thus activated titanium-silicates can be used for continuous operations, both in an isothermal suspended-bed reactor, equipped with stirring means, and in an adiabatic trickle bed reactor. A titanium-silicalite can be prepared by starting from several titanium sources (e.g., tetra-ethyl ortho-titanate, tetra-isopropyl ortho-titanate or peroxy-titanates optionally formed in situ and so forth), and from several silicon sources (tetra-ethyl ortho-silicate, silica sol and so forth). The product, obtained downstream the hydrothermal synthesis and the subsequent thermal treatments and treatments of activation with H.sub.2 O.sub.2, is microcrystalline. If the ammoximation process has to be accomplished in a trickle-bed reactor, a careful shaping of the catalyst is necessary, by resorting to further steps, such as pugging the titanium-silicalite with a suitable binding agent and then giving the mixture the shape of spheres, pellets, extrudates (optionally polylobate extrudates, having helical or non-helical grooves) and so forth. The Applicant has now developped a method allowing to obtain titanium-silicalite based catalysts, directly in sphere, pellet or extrudate shape, in an extremely simpler way.